1. Field of the Invention
The present invention relates to a cylinder identifying apparatus for combustion engine used to identify cylinders, to be controlled, of a multi-cylinder combustion engine.
2. Discussion of Background
In combustion engines, particularly combustion engines equipped in vehicles, an electronic controlling device, controlling injection timing and an injection quantity of fuel, ignition timing, and so on, for avoiding environmental contamination caused by exhaust gas and for improving economy such as an output characteristics with respect to fuel consumption. The electronical controlling device is further used to control various portions of the combustion engines. Therefore, the cylinders, to be controlled, are required to be controlled to perform these controls. FIGS. 8 through 14 explain an example of a structure and an operation of a conventional cylinder identifying apparatus for a combustion engine, wherein the combustion engine has four cylinders as an example.
In order to identify the cylinders to be controlled, a signal in synchronism with rotation of the combustion engine is used. Ordinarily, a crank angle signal, obtained from a rotational angle sensor located in a crankshaft or cam shaft of a combustion engine, is used. FIGS. 8 and 9 illustrate a structure of a first conventional combustion engine. Numerical reference 1 designates a crankshaft of a combustion engine (not shown) or a rotational shaft rotating in synchronism with a camshaft. Numerical reference 2 designates a rotational disk, fixed to the rotational shaft, wherein the rotational disk 2 has a plurality of windows 3 at predetermined positions, and one 3a of the windows is set to be asymmetric with the other windows 3. Numerical reference 4 designates a light-emitting diode (LED). Numerical reference 5 designates a photodiode receiving an output light from the LED 4 through the windows 3 and 3a. Numerical reference 6 designates an amplifier, amplifying an output signal from the photodiode 5. Numerical reference 7 designates an output transistor having an opened collector, wherein the output transistor works as a crank angle sensor 8.
In thus constructed crank angle sensor, when the rotational disk 2 rotates in synchronism with the crankshaft of the combustion engine, a signal illustrated in FIG. 10 is obtained in the photodiode 5 by the output light from the LED 4 through the windows 3 and 3a. The widths of the signals are respectively determined by lengths in a rotational direction of the windows 3 and 3a. These signals include a plurality of signals having signal widths of t0 corresponding to the windows 3, and a signal for identifying a specific cylinder having a signal width of t1 corresponding to the window 3a. Provided that the signal t1 for identifying the specific cylinder is provided for identifying a first cylinder, an order of the signals is, for example, a first cylinder, a third cylinder, a fourth cylinder, and a second cylinder, which is an order of igniting the combustion engine. For example, the signal t0 has a signal width between 75xc2x0 before top dead point, hereinbelow referred to as B75, and 5xc2x0 before top dead point, hereinbelow referred to as B5. For example, the signal t1 is set to have a signal width between B75 and 5xc2x0 after top dead point, hereinbelow referred to as A5.
FIG. 11 is a block chart illustrating a structure of a signal processing circuit. Numerical reference 8 designates the crank angle sensor described above. Numerical reference 9 designates an interface circuit, supplying the signal outputted from the crank angle sensor 8 in FIG. 10 to a microcomputer. FIG. 12 is a flow chart illustrating an operation of the microcomputer. The microcomputer 10 identifies the cylinders by receiving the signals illustrated in FIG. 10 as follows.
In Step 101, a width t1 or t0 of a high level portion of the signal inputted from the crank angle sensor 8 and a period T of the signal from a previous rising-up and a present rising-up of the signal are measured, where, Hereinbelow, the widths t1 and t0 are inclusively referred to as t. Succeedingly, a ratio t/T between the signal width t and the period T. measured in Step 101, is operated in Step 102. In Step 103, an average threshold value xcex1 n satisfying t0/T greater than xcex1 greater than t1/T is obtained from the result of t/T as follows:
xcex1n=(1xe2x88x92k)xcex1nxe2x88x921+k(t/T)n,
where reference k denotes a constant.
In Step 104, t/T obtained in the Step 102 and xcex1n obtained in the Step 103 are compared. When t/Txe2x88x92xcex1n greater than 0, the present signal width is determined to be t1 to know the specific cylinder. Thereafter, in Step 105, a cylinder identifying flag is set, when t/Txe2x88x92xcex1n less than 0, it is judged that the present signal is t0, indicating that the signal is not for the specific cylinder, the cylinder identifying flag is not set. In FIG. 10, the signal identifying flag is set in a control of the first cylinder, and thereafter the third cylinder, the fourth cylinder, and the second cylinder are sequentially controlled in the order of igniting the combustion engine with respect to succeeding signals.
FIG. 13 illustrates a schematic structure of a second conventional cylinder identifying apparatus. In the second conventional apparatus, a crank angle sensor 11 includes a rotating magnetic material 12 having a plurality of protruding teeth 12a around an outer periphery thereof, the rotating magnetic material 12 is attached to a cam shaft, rotating in synchronism with a crankshaft of a combustion engine, and a signal generator 13, arranged with the teeth 12a with a gap, for generating a signal depending on a change of a magnetic resistance of the gap, wherein the signal from the crank angle sensor 11 is supplied to a microcomputer 10 through an interface circuit 9.
The teeth 12a formed in the rotating magnetic material 12 are arranged with, for example, an interval of 10xc2x0 of a rotational angle of the crankshaft. As illustrated in FIG. 13, in predetermined positions, the teeth 12a are thinned out such that an interval between adjacent teeth 12a is 30xc2x0 in a portion 12b, an interval between adjacent teeth 12a is 30xc2x0 in a portion 12c, and the portions 12b and 12c are continuous to lack a signal pulse waveform, generated by the signal generator 13 at these portions.
The signal waveform is illustrated in FIGS. 14a and 14b, wherein a case that a first cylinder and a fourth cylinder are simultaneously ignited, and a second cylinder and a third cylinder are simultaneously ignited is illustrated as an example. FIG. 14a shows a signal waveform inputted in the microcomputer 10 from the crank angle sensor 11 through the interface circuit 9, wherein signals are pulses having an interval of 10xc2x0. In portions corresponding to the first and fourth cylinders, there is the thinned-out portion of 30xc2x0 just before the signal at B35, and two continuous thinned-out portions exist just before and just after the signal B35 at the second and third cylinders.
The microcomputer 10 operates each signal interval, and judges which signals belong to a group of the first and fourth cylinders or a group of the second and third cylinders depending on a ratio between a previous signal interval and a present signal interval, counts these signals to detect B75 signal and B5, starts processing of an ignition timing and a fuel injection timing, as illustrated in FIG. 14b, and resets counting-up after counting signals corresponding to two revolutions of the crankshaft in order to prepare for processing of coming two revolutions.
However, in the conventional cylinder identifying apparatuses, when a noise signal is superposed on a nomal signal by a noise from a power source, determination of the cylinders by a signal width and a signal interval becomes erroneous, and a fuel is supplied to wrong cylinders and wrong cylinders are ignited, whereby troubles such as backfire may occur. Therefore, in the conventional apparatus, a means for preventing an erroneous operation by circumventing the cylinder identifying operation is effected when an impossible signal in operating the combustion engine, for example, a case that signals having a signal width and a signal interval, corresponding to 18,000 rpm are inputted in the microcomputer 10. However, there is a case that a noise and so on, caused along with a drop of a power source voltage at time of cranking of the combustion engine superpose on the normal signal. In this case, it is impossible to circumvent the signal identifying operation in the conventional techniques because a waveform of the noise does not look like a high revolution. Because of insufficient identification of the cylinders, many troubles occur just after starting the cranking.
It is an object of the present invention to solve the above problems inherent in the conventional technique and to provide a cylinder identifying apparatus for combustion engine, which can securely identify cylinders at time of cranking the combustion engine and does not erroneously detect, erroneously control, or caused a delay in detecting the cylinders.
According to a first aspect of the present invention, there is provided a cylinder identifying apparatus for a combustion engine comprising: a crank angle sensor, detecting a crank angle of the combustion engine having a plurality of cylinders; a cylinder identifying means, identifying a cylinder to be controlled based on an output signal from the crank angle sensor; a cranking judging means, detecting a cranking state of the combustion engine; and an erroneous cylinder identification preventing means.
According to a second aspect of the present invention, there is provided a cylinder identifying apparatus for a combustion engine comprising: a crank angle sensor, detecting a crank angle of a combustion engine having a plurality of cylinders; a cylinder identifying means, identifying a cylinder to be controlled by an output signal from the crank angle sensor; a cranking judging means, detecting a cranking state of the combustion engine; and an erroneous cylinder identification preventing means, detecting starting of cranking of the combustion engine from an output from the cranking determining means, and circumventing identification of the cylinder by the cylinder identifying means when it is detected that a signal interval of the output signal from the crank angle sensor is a predetermined value or less in a predetermined time after the starting of the cranking.
According to a third aspect of the present invention, there is provided a cylinder identifying apparatus comprising: a first crank angle sensor, detecting a crank angle of a combustion engine having a plurality of cylinders and outputting a crank angle signal; a second crank angle sensor, detecting the crank angle of the combustion engine and outputting another crank angle signal having a mode different from the output signal from the first crank angle sensor; a cylinder identifying means, identifying a cylinder to be controlled by the output signals from the first crank angle sensor and the second crank angle sensor; a cranking judging means, detecting a state of cranking of the combustion engine; and an erroneous cylinder identification preventing means, detecting the cranking state of the combustion engine from an output from the cranking judging means and circumventing one of two events of cylinder identification based on the crank angle signals from the first and second crank angle sensors before the one of the two events of the cylinder identification is established.